An adaptive sliding mode control system for the excavator manipulator during straight-line digging operation was presented in this paper. The adaptive laws derived from Lyapunov stability theorem were used to update switching gains and compensate uncertainties. The dynamic model of the excavator manipulator considering link shape and weight was established and the straight-line trajectory of the bucket tooth tip of excavator was transformed into the desired joint angle trajectory for direct control. Finally, simulation results showed the superiority of the proposed control scheme compared with traditional variable structure control with sliding mode.